1. Field of the Invention
This invention relates generally to transmitting voice telephone calls over Internet Protocol (“IP”) based networks.
2. Discussion of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One of the paramount challenges facing modem wireless telephone systems is the rapid growth of consumer demand for data services, such as Internet access, text messaging, and e-mail. In fact, consumers are demanding greater access to data related services than ever before, and this trend is not likely to change. For example, in the coming years, consumers will likely expect their wireless telephones to provide many, if not all, of the communications features currently provided by computers communicating over wireline, (e.g., video conferencing, picture mail, etc.). Unfortunately, building or upgrading the wireless telecommunications infrastructure is relatively expensive.
Voice over IP (“VoIP”) is one of many recent wireless telephone advances that may challenge the capacity of the existing wireless communication infrastructure. VoIP systems move the routing of audio telephone calls away from conventional circuit switching networks to packets-based systems. One of the advantages of VoIP is that the IP packets that carrying the voice, referred to as VoIP packets, can be routed over a packet-based networks, such as the Internet or a cellular data network. Unlike conventional circuit switching phone systems that employ a constant connection during telephone calls, VoIP systems only send voice data packets across the network as they are needed. For example, VoIP packets are created and transmitted at the moment a user talks but not when the user listens or either end is in silence. As such, networks that employ VoIP systems may be able to support more telephone conversations over the same bandwidth as conventional circuit switched systems.
Employing VoIP systems in wireless network presents additional challenges that ay be not found in wireline VoIP systems. Most VoIP systems combine small pieces f telephone audio with a header, referred to as the “inner header,” that contains network routing for the telephone call and quality of service (QoS) information to create VoIP packets that can travel via the Internet. With wireless VoIP system, however, the VoIP packets also have to traverse through the wireless network, referred to as the Radio Access Network (“RAN”), to reach the Internet. In order to navigate the RAN, the VoIP packets are encapsulated with a second set of headers, known as the “outer header,” that contain network information for the RAN. After the VoIP packet navigates through the RAN to the Internet, the outer header can be removed from the VoIP packet. The VoIP packet may then travel through the Internet to the intended recipient of the telephone call. When the VoIP packet reaches its intended destination, the telephone audio from a plurality of VoIP packets are reformed and the original telephone conversation is reconstructed with a voice decoder.
In a typical VoIP packet, however, the headers may occupy a significant percentage of the overall VoIP packet size—fifty percent or more in some cases. For example, in the IPv4 standard, approximately sixty percent of each VoIP packet is used by the headers. Similarly, in the IPv6 protocol, approximately seventy percent of the total packet size is used by the headers. Using sixty percent or more of each VoIP packet to transmit headers, however, is inefficient. This inefficiency is especially significant in the RAN, because the backhaul bandwidth of the RAN is typically limited. For example, a typical RAN may employ relatively low bandwidth T1 lines to link components together. As such, it would be advantageous to be able to reclaim some percentage of the VoIP packet space occupied by the headers.